“We’re down to one volunteer a day,” says Janet Fritsch, chair of the PTO Thrift Shop. “We used to have ten or fifteen.” The shop, which raises money for PTO and booster groups in the public schools, lost most of its volunteers in March, when it posted a notice that parents could no longer earn money toward their own children’s school trips by working there. Some moms and dads saw the notice as they were signing in, Fritsch says, and “just walked out.”

The memo reflects a longstanding IRS rule that prohibits nonprofits from targeting benefits to individuals—one the shop had been blissfully unaware of till someone inquired and a lawyer was consulted. The shop was complying, Fritsch says, but some groups that sent volunteers were not. At about the same time, other requirements also turned off volunteers—a mandatory orientation and a rule that young students had to get a work permit before volunteering.

Fortunately, sales remain strong. The shop made $453,310 in sales in 2007, and “a good deal more” last year, says Fritsch. It already uses about 10 paid staffers—and will add more if new volunteers don’t step up soon.